I. Field of the Invention
The present invention relates to a transport device for the reading of identification cards such as I.D. cards, credit cards and the like (hereinafter referred to as ID cards) through linear movement of the cards, introduced through a feeding slot, by means of a conveyor belt which carries them past the reading device.
II. Description of the Prior Art
Transportation devices of this kind are used, for example, in automatic vending machines or ID card checking devices or in self-serve equipment. With their aid, ID cards which carry visible or invisible information symbols, can be carried past reading devices in order to determine whether the card carrier is entitled to perform certain actions and/or the amount up to which his credit is good. The interpretation device works, depending on the type of ID card information, according to the electro-magnetic, electrostatic or optical principle. When ID cards are transported past the device, they must have a precisely prescribed orientation in order to avoid faulty interpretation. Within this context it is also necessary that the card be kept a uniform distance from the checking unit in order to achieve similar signal amplitudes for like information symbols, especially when an electronic reader is used.
The ID or credit cards usually consist of plastic and are relatively sturdy so that they cannot be bent or cracked. It has become apparent, however, that through age and repeated use the cards can bend so that during transport past the reading device their distorted shape can result in faulty orientation in relation to the control device and also the distance from the device might be inaccurate. This makes it necessary that the transport device be so designed that even bent and deformed cards are taken past the reading device in straight formation.
The prior-known devices for this purpose are equipped (at least in the vicinity of the reading device) with costly roller mechanisms which consist of a number of rollers which exert their effects on both longitudinal edges of the card. Such roller conveyors are suited to keep the longitudinal edges of the cards straight, but cannot prevent a bending, for example in cross direction, of the remaining portion of the card, so that they can perform their task to guarantee a reliable evaluation only in those cases in which the checking device is close to the longitudinal edge which is being transported by the roller mechanism. Moreover, such roller mechanisms have a tendency toward operational trouble because cards can bend and wrap themselves around the various rollers so that it becomes necessary to open the entire transport unit in order to correct a malfunction.
It is also possible to use a conveyor belt for the transport of the ID cards and in this way the design of the moving elements can be kept simpler and less costly. The conveyor belt is, however, not suited for a firm grip on the cards, but only fit--by its nature--to transport cards that lie on top of the belt past a reading or checking device.
Interruptions of operation due to bent cards in rollers cannot occur as in systems with roller mechanisms. Since belt-systems are simpler and cheaper to produce, they should be preferred in reading ID cards, but should provide at least the same accuracy as the systems with roller mechanisms.